CODEWITHSUNDEEP
pythoncdistutilspython-c-extension
MFigueredo
MFigueredo

Reputation: 153

Using multiples C codes in one extension module Python

I have used C code in a Python project like in this tutorial. I built an extension so that it was possible to call the A function present in the main.c code through Python. However, function A calls other various functions that are present in a file called code.c, and I'm having trouble using those functions.

There are no problems if all the functions are placed in main.c, but I would like to modularize this project for organizational reasons!

The setup.py for building the modules is as follows.

ext       =  [
                 Extension(
                 'main',
                 sources = ['main.c'] ,
                 extra_compile_args=['-lpq'] ,
                 extra_link_args = ['-L/usr/local/pgsql/lib','-lpq'],
                 language=['c']
                 )
            ]

setup(name='project', version='1.0', ext_modules = ext)

How could I modify it so that the code.c functions could be used inside main.c without any problems?

Here is an outline of the situation:

main.c

#include <Python.h>
#include "code.h"

//....

void send(char* name)
{
   //DO SOMETHING
   function_from_code(name)
}

code.c

.....

#include "code.h"

void function_from_code(char* name)
{
   //DO SOMETHING
}

and then the Python code:

import main

...

main.send("My Name")

So in this way, the python code calls the function of module main C (so far so good). At the moment main.c calls a function from code.c, it throws the following error:

ImportError: /usr/local/lib/python2.7/dist-packages/main.so: undefined symbol: function_from_code

Apparently, using #include is not enough.

Upvotes: 1

Views: 54

Answers (1)

MSeifert
MSeifert

Reputation: 152587

This is too long for a comment and I'm not sure that it will fix the problem. I think it's just because it doesn't compile code.c and code.h when they are not listed explicitly as source (see "Extension names and packages").

Personally I would use either the depends argument for the Extension: 

from glob import glob

ext =  [Extension('main',
                  sources=['main.c'] ,
                  depends=glob('*.c') + glob('*.h'),
                  extra_compile_args=['-lpq'] ,
                  extra_link_args=['-L/usr/local/pgsql/lib','-lpq'],
                  language=['c']
                  )
        ]

or list all the files in source:

ext =  [Extension('main',
                  sources=['main.c', 'code.h', 'code.c'] ,
                  extra_compile_args=['-lpq'] ,
                  extra_link_args=['-L/usr/local/pgsql/lib','-lpq'],
                  language=['c']
                  )
        ]

Not sure if the order of the source files or depends files matters...

Upvotes: 1

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